Ammunition



J. D. HOWELL AMMUNITION Oct. 27, "l 953 Filed D80. 13, 1945 INVENTOR JOHN 0. Ho wa L AGENT Patented Oct. 27, 1953 UNITED STATES ATENT OFFICE AMMUNITION corporation of Delaware Application December 13, 1945, Serial No. 634,743

This invention relates to projectiles and, in particular, to an improved device for arming explosive and pyrotechnic projectiles. More especially, the invention relates to an improved detent for use in a projectile embodying a rotor type fuse.

The projectile shown and described is a small arms bullet, but it will be understood that this is for the purpose of illustration only and that the invention may be used with other types of fused projectiles and includes all modifications within the scope of the appended claims.

Fuses of various types have been used extensively in projectiles of large caliber shells and to some extent in the projectiles of cartridges of small caliber, such as 20 mm. cartridges and the 12 mm. cartridges used by both the Germans and Japanese. A more recent development is a 20 mm. cartridge embodying a rotor type fuse which, briefly, comprises a truncated sphere freely mounted in a substantially rectangular slot in the nose or cap of the projectile. The axis of rotation of the rotor passes through the geometrical center of the two flats of the rotor and is disposed at right angles to the longitudinal axis of the projectile. An aperture is provided in the rotor to receive a detonator, the axis of the aperture being substantially perpendicular to the axis of rotation of the rotor. On firing the cartridge, the rotation or spin of the projectile about its longitudinal axis sets up an unbalanced force couple in the rotor which swings the latter about its axis of rotation so as to arm the projectile by aligning the detonator with a firing pin provided in the end of the cap. Normally, however, that is to say, before the projectile has been fired, the detonator is held out of axial alignment with the firing pin by providing a suitable detent which temporarily holds the rotor from turning about its axis.

One type of detent currently in use comprises a substantially rectangular block supported to slide freely in a longitiudinal slot in the fuse cap, the slot being asymmetrical with respect to the longitudinal axis of the projectile. The slidable block has a laterally projecting shear pin arranged to engage in an aperture of the rotor to temporarily hold the latter from rotating. When the projectile is fired, the inertia of the block is sufiicient to cause the block to set back or slide rearwardly in its slot relative to the rotor and thus shear ofi the pin and free the rotor.

Although this type of detent has had some use, it embodies a number of closely fitting parts which are expensive to manufacture and difiicult.

2 Claims. (Cl. 102-80) 2 to assemble. Moreover, the design of the detent is basically undesirable in that the parts are asymmetrical with respect to the longitudinal axis of the projectile and, hence, interfere with the balance and accuracy of the projectile during flight.

An object of this invention is to provide an improved fuse for projectiles and, more especially, an improved device to prevent the fuse from arming until the projectile has safely traversed the length of the barrel. A further object is to provide a rotor type fuse with an improved detent which is simple to manufacture, simple to assemble and which is symmetrical with respect to the major axis of the projectile so as to insure the accuracy of the projectile during flight.

These and other objects, features and advantages of the invention will be described hereinafter in detail, reference being made to the ac companying drawing in which:

Fig. 1 is a side elevation in section of a projectile embodying the improved fuse assembly.

of this invention, the elements being in safe position.

Fig. 2 is a sectional view of the fuse cap before assembly on the body of the projectile and taken in the direction of arrows 2-2 of Fig. 1 showing the rotor and detent disk assembled in the cap. An aperture is shown in the rotor to receive a detonator.

Fig. 3 is an end view of the cap in the direction of arrows 3-3 of Fig. 2.

Fig. 4 is a side elevation of the rotor.

Fig. 5 is an end elevation of the rotor.

Fig. 6 is a fragmentary view of the projectile shown in Fig. 1, but with the elements of the fuse in armed position.

Referring to the drawing, the projectile shown in Fig. 1 comprises a hollow cylindrical body or core It], the heel end ll of which is of reduced diameter and provided with a knurled surface which, in the embodiment shown, comprises a. plurality of spaced bands [2 of knurling. A counterbore I3 is shown in the rear end of the core aperture. l4 and is adapted to receive relatively heavy material, such as lead granules or. lead slugs l5 for the purpose of providing a pro jectile of the proper weight. A standard sabot I6 is shown pressed over the heel end of the core to which it is firmly secured by the bands of knurling I 2. 1

The forward end of the core has a conical shoulder H, the base of which is spaced from aslightly tapered surface [8. adjacent the forward; end of the core, by an annular groove [9 having.

a relatively fine knurl 2|] in the bottom thereof. The central aperture l4 of the core is adapted to be substantially filled with an explosive or pyroteohnic charge and is provided with a depression at its front end for the purpose hereinafter described.

The nose portion of the projectile constitutes the fuse and comprises a cap indicated generally at 2! and which, in the present embodiment, is formed from a zinc blank by a cold extrusion process. It will be understood, however, that other materials and methods may be used for forming the fuse cap. The profile of the cap constitutes the ogive of the projectile and .before assembly on the core has a skirted base portion 22. When assembled on the core, the sklrt 22 will be blended into the taperedsu-rface 18 of the core as shown in Figs. 1 and 6. The caphas a relatively solid tip 23 provided with an axial firins pin aperture 24. Rearwardly of the solid tip 23 .is a recess indicated generally at 25 which is. open at its rear end and of substantially rectangular cross section, see Fig. 3. This recess comprises substantially parallelplanar side walls 26 (see Figs. 2 and 3) and top and bottom walls 21, the latter being of arcuate crosssection. "The forward end of the recess is substantially blind and comprises .a semicircular wall 28, see which is jformed by quadrants .21 of the upper and lower walls 21.. .An aperture 29 is provided in the forward wall of the recess in axial alignment with the .fir'ing pin aperture '24 and of slightly greater diameter so as to form a substantially square shoulder 13.0 with .the rear .end of the firing ,pin aperture 2.4.

The rear end of the recess opens into a relatively large counterbore .32, the forward end of which forms a substantially. square shoulder 33 with the rear end of therecesslii. .The profile of .the counterbore comprises a cylindrical wall section 34 .at ;the .forward end of the .counterbore, an annular.ribf.35 .ofrounded cross section at the rear end of the counterbore, corresponding .to the skirtedmortionll .of 1thecap, and ran annular taper 3.6 intermediate the cylindrical wall section and the annular rib.

Afiring 3.1 is shown .in .the aperture 2.4 .in the .nose of. the .cap. .In this embodiment, .the

jpin'3'l comprises a shank portion 3'! Which=make5 asmooth sliding fltintheaperturaz 4 .and which .is provided onits forward end with a radius. The rear end .of .the shank comprisesa conical detent 39 .having a substantiallysquare iflange 4.0 .atlitslbaselof greatendiameter .than' the firing pinaperture 32.4. Thefiring pinlis assembledin the nose of the cap by inserting the rounded end of theflring ,pininto .therear end .of .the firingpin aperturexand. sliding .the .piniorwardly until its flange 1'0 .abuts the shoulder "This construction. prevents the firmgpin from moving forwardly and Idroppingout .of .thenose of .the cap,the.1firing pin lbeing .enabled ,to move .rearwardly freely .on striking .a target so .as 110 .fire a detonator as hereinafter described.

' Mounted freely 'in the recess 2'5 ..is.a .ILQtor .43, see' Figs. 4Jan'd "5, which maybe 'formed .oflbrass or other suitable ,material and which. is shaped in general like" a truncated sphere 'having two flat substantially parallel surfaces i43"at opposite endsof =its minor axis mm). The latter is hereinafter referred to as the axis of-rotation of the rotor an'd, when-assembled in-the--cap,*is substantially 'perpen'dicular to the major axis of therprojectile. ""Thesgeometry' of the rotor is such that when itiis mounted m -the'-recess :0: the

- '4 cap, the flats 43 of the rotor are in juxtaposition to the corresponding planar side walls 26 of the recess 25 while the spherical surfaces 45 of the rotor fit into the arcuate top and bottom walls 21 and semicircular front wall 28 of the recess, as shown clearly in Figs. 1 and 2.

.As a substa tial y aperture 46 is pro-video on one or th ma o diameters of the rotor and is adapted to contain a detonator charge 4'1 which is held in the aperture by suitable sealing disks, such as foils 48. The density of the detonator charge 41 is different than the .densilty-of the material of the rotor 42 and hence insures a forceicouple to rotate the rotor in the manner hereinafter described.

Referring to Figs. 1 and 2, the periphery 15 of the rotor is provided-with two diametrically opposite pairs (of conical notches 49, each notch being adapted to receive the detent 39 of the firing pin. The arrangement ofrthese notches is shown in Figs. 1 .and 4 and is such that, when one of these notches is engaged .by thedetent of the firing pin, the longitudinal axis of the detonator {11 will be held at an angle of substantially 75 with the major axis ofthe projectile and out of axial alignment with the firing pin.

Suitable .means for holding the rotor forward in its recess "25 so that the detent 39 will fit in one of the rotor notches 49 is shown at 5'6 and comprises a detent washer having a concentric flash hole '52. 'The detent'washer {is preferably formed. of copper having a soft temper and isnormally convexin shape (seedottedlines in Fig. 2) and adapted to seat on the square shoulder 33 of the cap. During assembly of the fuse, as hereinafter described, .the convex washer is flattened thereby forcing 'the'peripheral edge of the washer tightly against thecylindrical wall section 34 of the counterbore so asto secure the washer firmly against the shoulder 33. In its assembled position, the flattenedbody portion of the washer-is in iuxtapositionto the rear end ofthe ro tor as shownjnFigs-l andZandserves to hold the rotor forwardly and to prevent rearward movement thereof fin its-recess 25. The'firing pin detent 39 will thusbe enabledito fully engage'in oneof-the conicalgnotches-41l of therotor to preventthe-latter ifrom rotating, about its -minor axis.

*The'assembly ofthe projectile andfuseis relativelysimpleand quickly accomplished. The-dew onator-mixture 41 is =loaded into the cylindrical aperture l'fi-oftherotor'and covered-at its-opposite ends with the seals or foils '48. IT-he firing -pin is inserted {into *the aperture inthenose ofjhe cap in the manner described above. Therotor is then -'inser ted into the rotor recess -25 and shaken gently until-one ofthe four conicalnotch es 49s1ipsoverthefiring pin detent-39. The flexiblewasherEEi isthen placedon-its seat with its convex side out and flattened, thus securing it firmly in place and holding 'the rotor forwardly in its -recess. The firing pin-detent, rotor-detonator, =and soft tenipered detent washer ;thus form-am integral-fuse-assembly-within;the cap 2 I The hollow body ofithe core to is; loaded-with its explosive e rpyrotechnic charge 53an'd a-suita-ble number 'of grainsof lead in 'theform of a leadslug or=-'slugs I 5 are provided in the tail-end .5 or 'proper1y:-weighting*the-proj ectile. It-will be notedthat there is a'slight depression 54 in the forward end-of thepowder charge. For successful operation, the powderadjacentthe clepressionii tshould be compressed hard enough: or: other means -provide'dzto hold tile -shape of the-depression so as to prevent 1 its -breakdown at any =time prior 4 to the arming of the projectile. The loaded core is then pressed heel end first into the sabot cup Hi. The fuse assembly is then secured to the core by supporting the cap, point down, in a profile die and pressing the forward end of the core into the rear end of the cap thereby to seat the conical shoulder I! of the core against the correspondingly tapered shoulder 36 of the cap; and to swage the skirted portion 22 of the cap inwardly radially so that its annular rib 35 looks securely in the annular knurled groove 19 of the core, its outer surface being blended smoothly into the external tapered surface 18 of the core.

The fuse of the projectile functions as follows: Immediately after firing the projectile the inertia of the relatively heavy rotor 42 exerts sufiicient force against the center of the relatively soft detent washer 50 to distort the washer as shown in Fig. 6 and release the rotor which moves rearwardly out of its recess 25. Rearward displacement of the washer and rotor is permitted by the depression 54 in the forward end of the powder charge 53, this depression being of such depth that the rotor 42 may set back sufficiently to disengage the firing pin detent 39 from one of the conical notches 49 of the rotor. The rotor is thereupon unlocked and free to rotate about its minor axis (11.). Initially, however. that is to say, while the projectile is moving down the first half of the barrel length, the acceleration of the projectile is so high and the centrifugal forces so low that the rotor is held back substantially immobile against the washer, this immobility of the rotor being further enhanced by the friction between the rotor and washer. Consequently, the rotor does not rotate into position to arm the projecile, i. e. to align the detonator with the firing pin. As the projectile passes through the second half of the barrel length, its acceleration decreases and the centrifugal force increases rapidly and reaches a magnitude such that an unbalanced force couple will be set up in the rotor, due to the difference in density of the rotor and its detonator, which will cause the rotor to turn. By properly proportioning the rotor 42 and initially setting the longitudinal axis of detonator 41 at an angle of substantially 75 with the major axis of the projectile, the projectile will have left the muzzle of the barrel by the time the detonator 41 is fully aligned with the firing pin 31. There is, therefore, no likelihood of the projectile exploding while still in the barrel of the firearm, that is to say, the projectile is bore safe. After leaving the muzzle of the firearm, the inertia of the rotor acting in conjunction with the deceleration of the projectile will cause the rotor to creep forwardly until the detonator is in contact with the firing pin detent and hence insure a supersensitive action. It is clear, however, that the projectile is safe against exploding by handling since the detonator 41 is normally securely held out of line with. both the firing pin 31 and the flash hole 52 of the detent washer until the projectile is armed. After the projectile has been armed and on striking a target the firing pin 31 and rotor 42 will be driven together violently, thereby exploding the detonator 41 and sending hot gases and flame through the flash hole 52 of the washer 50 to ignite the powder charge 53 within the core of the projectile.

What is claimed is:

l. A projectile fuse comprising a housing having therein a rearwardly opening recess and a forwardly opening aperture communicating with. said recess, a shouldered firing pin in said aperture and projecting into said recess, a rotor in said recess containing a detonator, and a. normally flat surfaced, edge supported soft metal disk press fitted into said recess in engagement with the rear portion of the rotor and normally holding said rotor in unarmed interengagement with said firing pin, said member being adapted for plastic deformation by the setback of said rotor incident to firing and to thereafter support said rotor free of said firing pin for centrifugal rotation to armed position.

2. A device according to claim 1 secured to a projectile containing a charge to be ignited by said detonator, the adjacent surface of such charge being of concave configuration and affording a support for said plastically deformable member when deformed.

JOHN D. HOWELL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,316,607 Watson Sept. 23, 1919 2,155,100 Scelzo Apr. 18, 1939 2,335,842 Nichols Nov. 30, 1943 2,441,939 Nichols May 18, 1948 

